1. Field of the Invention
The present invention relates to a golden-colored sintered product and a method of preparing the same. More specifically, the invention relates to a golden-colored sintered product having a high hardness, strength, Young's modulus (rigidity) and excellent oxidation resistance and corrosion resistance and is useful as a sliding material, golden-colored ornamental material exhibiting beautiful color tone and as an abrasion-resistant material for such applications as a wall material, a timepiece material, brooches, necklaces, medals, buttons, fishing tools and the like, and to a method of preparing the same.
2. Description of the Prior Art
As materials for ornamental purposes exhibiting gold color, there have heretofore been used a variety of metals such as pure gold, alloys thereof, brass and the like, as well as those metals of which the surfaces are plated with gold. However, these metals all have small hardnesses and get scratched on the surfaces or cracked when they come into contact with hard substances.
In order to solve such problems, there has so far been used the titanium nitride exhibiting high hardness, excellent oxidation resistance and beautiful gold color. To obtain the titanium nitride in the form of a sintered product, however, it must be sintered at a temperature which is as high as 2300.degree. C. or more in compliance with a particular method. Besides, the obtained sintered product has a low flexural strength and is brittle.
In recent years, therefore, there have been used sintered alloys of gold color obtained by bonding the titanium nitride with metals of the iron group such as nickel and cobalt (see Japanese Patent Publication No. 58335/1990).
When a sintering aid composed of a metal of the iron group is added to the titanium nitride, however, discoloration takes place due to, for example, sea water or sweat as the corrosion proceeds in the metal phase in the sintered product, and the color of the ornamental material is impaired. Moreover, the sintering aid exhibits poor wetting property with respect to the titanium nitride, whereby many voids appear in the whole crystals and grain boundaries, and vivid mirror surface is not obtained despite the mirror-surface polishing is effected.
Moreover, the sintered alloys obtained by adding metals of the iron group or other corrosion-resistant aids to the titanium nitride followed by sintering all exhibit Vickers' hardness of smaller than 1500 kg/mm.sup.2, which are not sufficient in terms of abrasion resistance and scratch resistance required for a variety of ceramic products and products having highly hard coatings which have been placed in the market in recent years.
With the sintered alloys using the above-mentioned metals of the iron group, furthermore, a sufficiently high Young's modulus is not obtained making the machining very difficult from the standpoint of, for example, obtaining a high dimensional precision required for the insertion products.
The present inventors have forwarded the study in order to solve the above-mentioned problems, and discovered the fact that a golden-colored sintered product having a sufficiently high strength, Young's modulus and excellent oxidation resistance and corrosion resistance is obtained when a titanium boride and a metal boron is added to the titanium nitride followed by sintering, without losing high hardness inherent in the titanium nitride.